Examples of workpieces are components of an automotive door-trim for an assembly line, or a semifinished door-trim assembly to be completely assembled. A conventional automotive door-trim assembly adapted to be used for an automated assembly line includes an upper door-trim and a lower door-trim, etc., as shown in, e.g., Japanese Early-Patent Publication No. 2004-224012. The upper door-trim has a laminated structure in which a scarfskin adhesive is placed on the surface of a resin core, and in which the lower door-trim is an injection-molded synthetic resin. To bring together the upper and lower door-trims, bosses for welding are provided on a rim of the lower door-trim to be coupled to the upper door-trim such that they stand along the rim with predetermined pitches therebetween. The bosses of the lower part are then inserted in holes for mounting are punched on the upper door-trim to form a semifinished door-trim assembly. The semifinished door-trim assembly is then loaded in an ultrasonic welding and bonding machine having clamps or metal braces clamping the upper and lower door-trim. In this state, the semifinished door-trim assembly is ultrasonically welded and bonded such that the upper and lower door-trims are coupled together.
When the ultrasonic welding and bonding is applied, if an undesirable gap forms between any boss and the periphery of the mated holes for mounting at the junction of them, this causes a space to occur between the upper part and the lower part of the door-trim at the junction of them, which degrades their adhesiveness. In practice, the peripheries of portions of the workpiece to be processed by the ultrasonic welding and bonding are clamped, to protect the peripheries from being lifted up, to avoid an undesirable gap. In addition, in an assembly line, processes for bending weather-strip claws, for inserting retainers, and for fastening threads, are also carried out, as well as the ultrasonic welding and bonding process being carried out.
In the conventional assembly line, holders for holding the workpieces are installed in an ultrasonic-welding and bonding machine, or in a machine for bending weather-strip claws, or a machine for inserting retainers. The holders have respective junctions dedicated to the corresponding machines. The clamps on the junctions of the holders are also dedicated ones designed based on the number of processes to be applied to the junctions of the respective machines on the line. Because the respective machines thus use the dedicated holders that are also dedicated and formed for the respective machines, no holder can share a machine on the same line. This causes problems involving the need to providing mechanisms to convey the workpieces between the respective machines on the same line, increasing costs to produce the respective machines and thus the door-trim assemblies to be assembled therefrom, and a setback in improving productivity.
Accordingly, an object of the present invention is to provide a jig pallet that can be shared in the assembly line, and that has a general versatility.